UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 1 of 17

 (U) Fire Extinguishing Agents for Protection of Occupied 

Spaces in Military Ground Vehicles

Steven E. Hodges, Ph.D.

Senior Scientist, Principal

Alion Science and Technology

Santa Barbara, CA 93105

steven.e.hodges1@us.army.mil

Steven J. McCormick

Team Leader, Damage Reduction

Army TARDEC Ground Systems Survivability 

Warren, MI 48397

steven.j.mccormick@us.army.mil

(U) ABSTRACT

(U) Historically the US Army (USA) used Halon 1301 

(bromotrifluoromethane), a chemical with high Ozone Depletion 

Potential (ODP), to protect the crews of armored vehicles from the 

effects of peacetime and combat fires. Since the phase-out of Halon 

production the USA has directed that zero ODP materials be used 

wherever possible. Subsequently, major new vehicle platforms have 

been deployed with Automatic Fire Extinguishing Systems (AFES) that 

rely on HFC-227BC, a zero-ODP-agent blend of HFC-227ea 

(heptafluoropropane) and sodium-bicarbonate-based dry chemical.

Unfortunately, hydrofluorocarbons (HFCs) generally have high Global 

Warming Potential (GWP) - thousands of times that of carbon dioxide on 

a weight basis. Hence, as part of a larger effort to reduce its carbon 

footprint, USA Program Managers have asked that more 

environmentally friendly fire extinguishing agents be evaluated as part of 

ongoing vehicle modernization efforts. Several agents are being 

investigated, including FK-5-1-12, water with additives, and dry 

chemicals. This report describes the findings of more than 150 live-fire 

tests using nine agents and four extinguisher technologies. The basic 

conclusion is that no alternate agent can yet be considered to be a drop-in 

replacement for Halon 1301 or HFC-227BC for this application.

However, a blend of Halon 1301 and dry chemical has been found to be 

about twice as effective as Halon 1301 alone. Thus, pending 

confirmation tests on vehicles, it may be feasible to use less Halon in 

legacy systems without compromising fire protection performance.

DISTRIBUTION A: Approved for Public Release; Distribution is Unlimited.
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 2 of 17

(U) INTRODUCTION

(U) By 1982 the first modern, automatic fire extinguishing system (AFES) designed to 

protect the crew from combat-induced fires was deployed on a US Army (USA) vehicle, the M1 

Abrams main battle tank. AFES are comprised of four major components: fast fire sensors, 

control electronics, fast-opening fire extinguishers, and integration wiring and bracketry (ref. 1, 

2). Subsequently, the USA fielded similar systems on other platforms including the Bradley 

Fighting Vehicle (BFV) and Field Artillery Ammunition Support Vehicle (FAASV).

(U) In Army tests, AFES were able to detect and suppress combat fires (i.e., fast-growth fuel 

oil deflagrations) in a fraction of a second (ref. 1, 2). In Desert Storm battle damage 

assessments, the systems were reported to have been effective (ref. 3). These systems all used 

extinguishers filled with Halon 1301 (bromotrifluoromethane). 

(U) In compliance with the requirements of the US Clean Air Act Amendments of 1990 and 

in conformity with the Montreal Protocol (MP) of 1987, Halon 1301was phased out of 

production at the end of 1993. Subsequently, the USA decided to use substances with zero 

ozone depletion potential (ODP) wherever possible. Since then, AFES have been deployed on 

STRYKER, Up-Armored High Mobility Multipurpose Wheeled Vehicles (Up-Armored 

HMMWV or UAH), Mine Resistant Ambush Protected (MRAP) vehicles and other platforms,

including the US Marine Corps‟ (USMC) Light Armored Vehicle (LAV) and Expeditionary

Fighting Vehicle (EFV). These AFES use similar detection and controls as used in older systems 

but rely on extinguishers filled with a more environmentally friendly agent: HFC-227BC (also 

known as FM-200BC), a blend of HFC-227ea (heptafluoropropane) and sodium-bicarbonatebased dry chemical. HFC-227ea, an HFC, has zero ODP so its continued production is 

acceptable under the MP. The blend was developed by the Army as part of an effort to find 

Halon-alternate fire extinguishing agents, and was demonstrated to be essentially as effective as 

Halon 1301 and adequate as a Halon replacement (ref. 4). The STRYKER Brigade Combat 

Team (BCT) was the first USA vehicle to be qualified with HFC-227BC as its crew agent (refs. 

5, 6). New vehicles, including Joint Light Tactical Vehicle (JLTV) and MRAP All-Terrain 

Vehicle (MATV), currently specify HFC-227BC for the crew AFES. Table 1 lists (in order of 

qualification) the agent used in the crew AFES of major USA and USMC platforms. The Army 

relies on its Halon reserve to support legacy vehicles. 

(U) However, HFC materials such as HFC-227ea have high Global Warming Potential 

(GWP) - thousands of times that of carbon dioxide. Hence, as part of a larger effort to reduce its 

carbon footprint, the USA has begun looking at more environmentally friendly fire extinguishing 

agents. Several agents are being evaluated, including FK-5-1-12, water with additives, and dry 

chemicals. This report describes the findings of that project based on more than 150 live-fire 

tests using nine agents and four extinguisher technologies. It should be noted that converting an 

existing system from one agent to another involves many steps, achieving acceptable fire 

suppression performance discussed in this paper being a key one. Other steps are listed in ref. 7.
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 3 of 17

Table 1. (U) Crew AFES agents in order of qualification.

Platform Crew AFES Agent

Abrams Main Battle Tank Halon 1301

Bradley Fighting Vehicle (BFV) Halon 1301

*Field Artillery Ammunition Support Vehicle (FAASV) Halon 1301

USMC Expeditionary Fighting Vehicle (EFV) HFC-227BC 

STRYKER Brigade Combat Team (BCT) HFC-227BC 

Up-Armored HMMWV (UAH) HFC-227BC 

Mine Resistant Ambush Protected (MRAP) HFC-227BC 

USMC Light Armored Vehicle (LAV) HFC-227BC 

MRAP All-Terrain Vehicle (MATV) HFC-227BC 

**Joint Light Tactical Vehicle (JLTV) HFC-227BC 

***Future Combat Systems (FCS) HFC-227BC 

*Upgrade to HFC-227BC in process **In development ***Manned Ground Vehicle Cancelled

Table 2. (U) Agent Properties. 

Property Halon 

1301

HFC227eaa FK-5-1-12b Water+

c Dry 

Chemicald

Environmental

Ozone Depletion Potentiale16 0 0 0 0

Global Warming Potentialf6900 3500 1 0 0

Atmospheric Lifetime (yr) 65 33 0.014 0 0

Safety

Design Concentration (%v/v) 5 8.7 6.7g~300 g/m3~300 g/m3

NOAELh(%) 5 9.0 10 NA TBDj

LOAELi(%) 7.5 >10.5 10 NA TBDj

Physical

Boiling Point (°C) -58 -16 49 115 N/A

Vapor Pressure @ 21°C (bar) 13.7 4.1 0.41 0.03 N/A

Liquid Density (g/cm3) 1.56 1.39 1.60 1.27 2.16

Molecular Weight (g/mol) 149 170 316 31 84

Heat of Vaporization (J/g) 117 132 88 >2250 N/A

a) HFC-227ea is a form of heptafluoropropane and is sold as a fire extinguishing agent. b) FK-5-1-12 is a 

perfluorinated six-carbon ketone manufactured and sold as a fire extinguishing agent. c) Water with 50% Potassium 

Acetate. d) Values given are for sodium bicarbonate-based dry chemical. Potassium bicarbonate crystal density is 

2.17 g/cm3. e) CFC11 baseline, ref. 8. f) CO2 baseline, ref. 9. g) Concentration advised by the agent manufacturer 

representative for this application. h) No Observed Adverse Effects Level. i) Lowest Observed Adverse Effects 

Level. j) Acceptable concentration levels for this application to be determined by the USA.
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 4 of 17

(U) Table 2 lists key properties for the basic agents used in the tests described in this paper. 

The agents that are mixtures of a fluorocarbon agent (i.e., Halon 1301; HFC-227ea; or FK-5-1-

12), and dry chemical have essentially the same environmental and safety properties as the base 

fluorocarbon agent. The environmental properties illustrate part of the motivation for this study: 

Halon and HFC-227BC, the agents currently used in Army crew systems, have high GWP, and 

Halon has a relatively high ODP so its production is prohibited by the MP and its use is limited 

by Army policy. FK-5-1-12 has zero ODP but a finite GWP – equivalent to carbon dioxide 

(CO2). A recent EPA finding has listed several Green House Gases (GHGs), including CO2, as a 

threat to public health (ref. 10) and recent legislation has proposed significant reductions in GHG 

production (ref. 11). Although future limitations on the use of near-zero GWP materials such as 

FK-5-1-12 are not anticipated, if limitations are imposed, they should be mitigated by the fact 

that relatively little FK-5-1-12 and similar fire suppression chemicals are emitted compared to 

CO2.

(U) APPROACH

(U) The Tank and Automotive Research, Development and Engineering Center‟s (TARDEC) 

purpose for the tests described herein was to compare the performance of deployed suppression 

agents and more environmentally friendly ones. Distinguishing the performance of the agents

was facilitated by operating close to where the extinguisher system is overmatched by the fire; 

the ideal was to bracket the fire with successful and failed suppression in a repeatable way for 

each agent tested. We therefore invited three extinguisher suppliers to support the tests – and 

asked them to provide suppression systems based on various agents and concentrations that 

would yield marginal suppression „passes‟ and „failures‟ based on current vehicle performance 

criteria. Note that the amount of agent used was often less than the design concentration used in 

production systems.

(U) The tests were conducted at the Army‟s Aberdeen Test Center (ATC) in a 260 ft3(7.36 

m

3

) box with relatively little clutter, no active air flow, and hatches closed (Figure 1). Although 

the exploratory test box volume is similar to some legacy vehicle crew compartment volumes, it 

does not represent a specific application. Tests were conducted at the outdoor ambient 

temperature at the test site which ranged from approximately 25 to 90°F (-4 to 32°C).

(U) Figure 2 shows the test box with sampling points, fire position and flame path, 

extinguisher positions and agent discharge directions indicated. 

(U) The test box was instrumented to measure blast overpressures, temperatures and the 

chemistry of the atmosphere, in particular the combustion byproducts. The response times of the 

thermocouples were too long to effectively measure the brief excursions that could have caused 

skin-burn injury – however they gave a gross indication of the air temperature. For this reason 

and because the thermal excursions measured were benign, those results are not reported. A 

high-speed video camera recorded the fire and its suppression from the top of the box.

(U) The fires were detected by a production infrared optical fire sensor that, via a simple 

controller, released the extinguishers. The average time to valve activation was approximately 

40 ± 5 ms after the first pressure and/or infrared signature was observed in the ballistic data. 
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 5 of 17

(U) The Field Chemistry Sampling and Analysis Team at ATC measured the combustion 

byproducts during the tests, including carbonyl fluoride (COF2) and hydrofluoric (HF) acid. The 

atmosphere was sampled from four positions within the test box (Figure 2). A technique

specifically developed by the ATC Field Chemistry group to distinguish FK-5-1-12 and COF2

(ref. 12) was employed. ATC subsequently reported the chemistry results (ref. 13) including 

casualty assessments for each test based on current vehicle performance criteria (ref. 14). 

Figure 1. (U) Exploratory Test Box a) Exterior and b) Interior.

Figure 2. (U) Extinguisher Positions, Blast Overpressure and Chemistry Sample Points in the 

Test Box. 
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 6 of 17

(U) The „Pass/Fail‟ criteria used are based on the current USA crew casualty criteria applied 

to armored ground vehicles. Table 3 lists major excerpts and derivations from the formal 

requirements (ref. 14). It is important to note that current criteria are under review and may be 

revised (ref. 15).

Table 3. (U) Selected Crew AFES Performance Criteria. 

Parameter Requirementa Testb

Fire Suppression Extinguish all flames without reflash Y 

Skin Burns Less than second degree burns 

(<2400°F-sec over 10 seconds or heat flux < 3.9 cal/cm2)

c

Overpressure Less than 11.6 psi Y 

Agent Concentration Not to exceed LOAELd Y 

Acid Gases 

(HF + HBr + 2∙COF2) Less than 746 ppm-min (5 min dose) Y 

Oxygen Levels Not below 16%e Y 

Discharge Impulse

Noise 

No hearing protection limit: <140 dBPf

Single hearing protection limit: <165 dBPf N 

Discharge Forces Not to exceed 8 g

g

and <20 psi at 5 inchesh N 

(a) Based on reference 14a except as noted. (b) Addressed in Exploratory Tests. (c) Temperature recorded with 

thermocouples. (d) Lowest Observed Adverse Effects Level per ref 16. (e) ref. 14b. (f) ref. 14c. (g) Extrapolated

from ref. 14a. (h) ref. 15.

(U) In industrial explosion protection tests, the volume-normalized speed of an explosion is 

often calibrated using a parameter called Kmax, defined as (ref. 17) 

3

max

max V

dt

dP K

(1)

where P is the blast overpressure, t is the time and V is the test box volume. The results for five 

baseline fire tests with no suppression yielded an average Kmax of 2.7 bar-meter/seconds with a 

standard deviation of 0.2. Due to significant fluctuations in the pressure traces after the agent 

and fire interact, and to better facilitate the „real-time‟ nature of these exploratory tests, a variant 

of Kmax given in equation (1) was used:

3 V

t

P

K

(2)

(U) In equation (2), ∆P is the pressure change during a time interval ∆t. In these tests, K was 

determined using a predetermined interval starting at the time the extinguishers were activated. 

The target for the fires was a K value of 1 to 2 bar-meter/seconds. 
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 7 of 17

(U) AGENTS AND EXTINGUISHERS

(U) Nine suppression agents were used (the short-hand names in parenthesis are used in 

subsequent charts and tables):

• Halon 1301 („Halon‟)

• Halon 1301 with Sodium Bicarbonate-based Dry Chemical („Halon+‟)

• Halon 1301 with Potassium Bicarbonate-based Dry Chemical („HalonK‟)

• HFC-227ea with Sodium Bicarbonate-based Dry Chemical („HFC227BC‟)

• FK-5-1-12 („FK-5-1-12‟)

• FK-5-1-12 with Sodium Bicarbonate-based Dry Chemical („FK-5-1-12+‟)

• Water with Potassium Acetate-based additives („Water+‟)

• Sodium Bicarbonate-based Dry Chemical („NaBC‟)

• Potassium Bicarbonate-based Dry Chemical („KBC‟)

(U) As indicated in Table 1, Halon 1301 is used in the crew compartment of legacy vehicles 

such as the Abrams and Bradley. „Halon+‟ is a mixture of Halon 1301 and sodium-bicarbonatebased dry chemical. Although never fielded, this mixture is expected to be compatible with most 

or all fielded hardware, in which case current Halon 1301 extinguishers could be recharged with 

„Halon+.‟ „HFC-227BC‟ is also a mixture of a clean agent and sodium-bicarbonate-based dry 

chemical. A specific blend of HFC-227BC (i.e., HFC-227ea with 5% by weight dry chemical) is 

fielded in the AFES used to protect the crew in STRYKER (refs. 5, 6, 7), Up-Armored 

HMMWV, MRAP, upgraded FAASV, and the USMC‟s Expeditionary Fighting Vehicle (EFV)

and Light Armored Vehicle (LAV). Some MRAP vehicles allow up to 10% by weight dry 

chemical.

(U) The amount of sodium bicarbonate-based dry chemical added to the clean agents tested 

varied from 5% by weight, the usual fielded mix, to a much higher fraction. Crew AFES based 

on HFC-227BC use a HFC-227ea design concentration of about 9% by volume at 20°C – a level 

that ensures the LOAEL is not exceeded at temperature extremes. In such a system, a 5% by 

weight mix of sodium bicarbonate corresponds to a dry chemical density of 40 g/m3in the 

protected volume. The Army specifies a 5 to 10% by weight mix of dry chemical in HFC227BC systems. Therefore, the maximum amount of dry chemical additive used in the tests 

described herein was 80 g/m3.

(U) FK-5-1-12 is widely available but has never been fielded in an Army crew-AFES. 

Although the „FK-5-1-12+‟ mixture was tested, FK-5-1-12 and sodium-bicarbonate-based dry 

chemical interact chemically and so cannot be stored together for long periods of time as is done 

with HFC-227ea and dry chemical. However, the chemical interaction between FK-5-1-12 and 

the dry chemical did not appear to be significant in the brief period they were stored together for 

the tests described herein.

(U) An industrial explosion protection study concluded that, given the phase-out of Halon, 

sodium-bicarbonate-based dry chemical offered “the best compromise between effectiveness and 

practical acceptance for all but the special cases of occupied spaces” (ref. 18). No discussion or 

reference is given for why dry chemical is not an acceptable agent for occupied spaces; it may be 

due to the common-sense bias against breathing dust. In any case, the sodium-bicarbonate-based 
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 8 of 17

dry chemical used in the test series described herein (ref. 19) was previously found to be 

acceptable for use in crew compartments by the USA (ref. 20). When dry chemical was tested 

alone, the concentrations used were as high as 300 g/m3, higher than the levels seen in fielded 

HFC-227BC systems (40 to 80 g/m3based on a 5 to 10% by weight dry chemical to HFC-227ea

mix, with the HFC-227ea at the maximum safe level). Operational issues including clean-up and 

obscuration remain to be fully addressed (ref. 21).

(U) This study also compared potassium bicarbonate (ref. 22) and sodium bicarbonate, both 

as sole suppression agents and as additives to Halon 1301. Previous studies have found that for 

certain types of fires, potassium-based dry chemical can be as much as twice as effective as 

sodium-based dry chemical by weight (ref. 23). Consequently, in the tests described herein, 

suppression performance was compared with half the potassium-based agent with respect to the 

sodium-based dry chemical.

(U) „Water+‟ is a 50-50 mix of water and potassium acetate. This mix is available 

commercially (for example it is used for de-icing operations at airports), and was one of two 

agents TARDEC originally recommended as a Halon 1301 replacement (ref. 4). However,

special care must be taken to prevent reflash fires when integrating a water-based AFES (ref. 4). 

In addition, operational issues, such as clean-up and effects on electrical equipment, remain to be 

fully addressed.

(U) Agents were delivered by four extinguisher configurations from three independent 

suppliers:

• Nitrogen charged cylinder with a solenoid valve (used in Abrams, BFV, FAASV, 

STRYKER, UAH, and some MRAPs); „N2 Solenoid‟ in Table 4

• Nitrogen charged cylinder with a linear actuated valve (designed for use in the crew and 

mission bay of FCS‟ NLOS-C); „N2 Linear‟ in Table 4

• Nitrogen charged cylinder with a squib actuated valve (used in some MRAPs); „N2

Squib‟ in Table 4

• Gas Generator driven Hybrid Fire Extinguisher (developmental); „GG HFE‟ in Table 4

(U) DESCRIPTION OF TESTS AND RESULTS

(U) A total of 157 live-fire tests in four series were conducted in the December 2008 through 

September 2009 period. Each test used two equivalent extinguishers (in positions 1 and 2 

indicated in Figure 2) unless otherwise noted.

(U) The agents and extinguisher configurations tested are summarized in Table 4. Table 5

shows the best results obtained for each agent; note that the best performance and minimum 

agent weights are not obtained simultaneously. The agent weight listed is the least used while

obtaining a reliable (e.g., repeated) „pass.‟ Both tables show the number of „passes‟ obtained –

agent quantities were adjusted to try to achieve „passes‟ in half the tests. Table 6 summarizes the 

failure mechanism(s) (i.e., limiting criteria) for each agent tested.
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 9 of 17

Table 4. (U) Exploratory Test Result Summary by Extinguisher, Agent, and Hardware.

Agent N2 Solenoid N2 Linear N2 Squib GG HFE 

Total 

Tests

*Total 

‘Passes’

Halon 19 0 0 2 21 12 (57%)

Halon+ 19 0 0 0 19 16 (84%)

HalonK 7 0 0 0 7 4 (57%)

HFC-227+ 16 8 1 11 36 17 (47%)

FK-5-1-12 10 0 4 7 21 0

FK-5-1-12+ 6 0 2 7 15 0

Water+ 12 0 1 10 23 12 (52%)

NaBC 13 0 0 0 13 7 (54%)

KBC 2 0 0 0 2 2 (100%)

TOTAL 104 8 8 37 157 70 (45%)

*The goal for each agent was to pass half the tests.

 

Table 5. (U) Exploratory Test Result Summary Showing Best Results for Each Agent. 

**Performance

Agent Total *Pass

**Least 

Agent 

Weight 

(lb)

Lowest 

Acid Dose 

(ppm-min)

Lowest 

Pressure 

Peak (psi)

Fastest 

Fire Out 

Time (ms) Note

Halon 21 12 ~5 ~500 <1 <200 Legacy fielded product

Halon+ 19 16 ~2.5 <20 <1 <200

New mix compatible with 

fielded extinguishers

HalonK 7 4 ~2.5 <20 <1 <200

New mix compatible with 

fielded extinguishers

HFC227BC 36 17 ~5 <20 <1 <200 Fielded product

FK-5-1-12 21 0 >25 ~2,000 1.2 <200 Available

FK-5-1-12+ 15 0 >15 ~1,300 1.6 <200 Invention required

Water+ 23 12 ~4 0 1.5 ~400

Development required; 

operational issues?

NaBC 13 7 ~3 0 <1 <200

Available; operational 

issues?

KBC 2 2 ~2 0 <1 <200

Available; operational 

issues?

Total 157 70

*The goal for each agent was to pass half the tests. **Best Performance and Least Agent Weight are not obtained 

simultaneously. Acid doses are obtained from ref. 13.
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 10 of 17

Table 6. (U) Summary of Limiting Criteria for Agents Tested.

Agent Limiting Criteria Collateral Criteria Other Issues

Halon Acid Gas Pressure & Temperature Deployed & Stockpiled

Halon+, K Pressure Acid Gas & Temperature New Agent Mix

HFC227BC Acid Gas & Reflash Pressure & Temperature Deployed

FK-5-1-12 Acid Gas Reflash Weight 

FK-5-1-12+ Acid Gas Reflash Weight, Agent Compatibility

Water+ Reflash Pressure & Temperature Clean-up

Dry Chem Reflash Pressure & Temperature Obscuration & Clean-up

(U) Figure 3 shows the acid-gas dose measured versus the amount of agent released for all of 

the fluorinated agents for one of the extinguisher configurations. The maximum acceptable acid 

dose and safe agent weights are also indicated. The minimum measurable acid dose was 20 

ppm-min.

Figure 3. (U) Average Acid Dose Integrated over 5-Minutes versus Agent Density (ref. 13d,e). 

The solid line is a „best fit‟ trend using a Power Series based on the „HFC-227BC‟ data.

(U) The „FK-5-1-12‟ and „FK-5-1-12+‟ tests with approximately 25 pounds of agent used 

equivalent extinguishers in all three locations shown in Figure 2. The relative trends for „FK-5-

1-12,‟ „FK-5-1-12+‟ and „HFC-227BC‟ indicated in Figure 3 were observed for all extinguishers 

tested with those agents. 
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 11 of 17

(U) Interestingly, the Halon 1301 results shown in Figure 3 indicate little or no advantage to 

using maximum safe concentrations. The high acid levels measured are consistent with earlier 

results (ref. 4) and indicate that the test fire is nearly an overmatch of the Halon systems 

described herein. 

(U) Halon+ and HalonK agents were tested with one (in position 2) and two (in positions 1 

and 2) extinguishers per test, as parenthetically indicated in Figure 3. None of the tests using 

two extinguishers failed, even when very low Halon concentrations were used. Consequently, 

tests with a single extinguisher were necessary to achieve the desired failures. Note that one of 

the four „Halon+(1)‟ tests using sodium-bicarbonate-based dry chemical „passed,‟ while none of 

the three „HalonK(1)‟ tests, using approximately half the amount of potassium-bicarbonate-based 

dry chemical, „passed.‟ This suggests that, when mixed with Halon, potassium-bicarbonatebased dry chemical is not significantly more effective that sodium-bicarbonate-based dry 

chemical.

(U) Figure 4 shows the acid gas dose versus minimum oxygen levels observed for the tests 

using Halon with potassium-bicarbonate and sodium-bicarbonate-based dry chemical additives.

The results indicate that the test fires were limited by the amount of oxygen (versus fuel) 

available and clearly distinguish the „Passes‟ and „Fails.‟ Also indicated is that, in a failed 

suppression, potassium-bicarbonate-based dry chemical with Halon yields somewhat lower acid 

than Halon with sodium-bicarbonate-based dry chemical.

Figure 4. (U) Five-Minute Acid Dose versus Minimum Oxygen Level for Halon with Sodiumand Potassium-Bicarbonate Dry Chemicals (ref. 13e).

(U) Figure 5 compares the integrated blast overpressure versus agent mass density for all 

agents tested. Although integrated pressure is not a casualty criteria, because the „passes‟ and 

„failures‟ based on established casualty criteria are distinguished using this parameter, it is a 

convenient method for comparing fluorinated agents that produce acid gas with nonfluorinated 

agents that do not produce acid gas. The threshold between a „pass‟ and a „fail‟ appears to be 
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 12 of 17

about 0.2 bar-s. It is interesting to note that Halon and HFC-227BC fail at agent densities of a 

little less than 0.25 kg/m3; the other agents described herein (except for the FK-5-1-12-based 

agents) appear to require densities of at least 0.15 kg/m3. Because the FK-5-1-12-based agents 

yielded unacceptably high acid levels at the maximum safe concentration (as shown in Fig. 3), 

they were not tested at low concentrations where a failed suppression resulting in high integrated 

pressures would have occurred.

(U) Figure 5 includes the results for dry chemical agents alone, and allows another 

comparison of sodium-bicarbonate- and potassium-bicarbonate-based dry chemicals: When 

mixed with Halon, the potassium-based dry chemical performs about the same as the sodiumbased dry chemical, consistent with the results shown in Figures 3 and 4. However, when used 

alone, the potassium-based dry chemical („KBC‟) is almost twice as effective by weight 

compared to sodium-based agent („NaBC‟), consistent with earlier findings (ref. 23).

(U) The „Water+‟ tests using proprietary (non-production) distribution systems performed 

about as well as other agents on a weight basis as indicated in Figure 5. The successful „Water+‟ 

tests resulted in fire-out times about twice as long as the other agents, as indicated in Table 5. 

However, other suppression parameters were comparable to the other agents.

Figure 5. (U) Integrated Blast Pressure versus Agent Density for Halon with and without Dry 

Chemical Additives, HFC-227BC, Sodium- and Potassium-Bicarbonate Dry Chemicals and 

Water with Freeze-Point Suppressant. The arrows indicate the minimum agent densities required 

for successful suppression.
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 13 of 17

(U) DISCUSSION

(U) A few observations can be made based on the results described above:

Figure 3 indicates that Halon 1301 and HFC-227BC performed similarly, although Halon 

1301 yielded relatively higher acid doses, consistent with earlier findings (ref. 4).

Tables 4 and 5 show that FK-5-1-12 was not effective whether used alone or mixed with 

dry chemical due to high acid gas levels.

Tables 4 and 5 and Figure 5 indicate that dry chemical and water with additives may 

become viable but further analysis, development and testing are required.

Figure 5 indicates that when used as the sole suppression agent, potassium-bicarbonatebased dry chemical is almost twice as effective by weight as sodium-bicarbonate-based 

dry chemical, consistent with earlier findings (ref. 23).

Figures 3, 4 and 5 indicate that the mixes of Halon with sodium- or potassiumbicarbonate-based dry chemicals performed similarly.

Figures 3 and 4 indicate that Halon with sodium- or potassium-bicarbonate-based dry 

chemicals is twice or more as effective by weight as currently deployed crew agents 

(Halon and HFC-227BC). This result needs to be verified in vehicle-level tests.

None of the non-Halon agents as evaluated are drop-in replacements (i.e., have the same 

form factor and comparable performance) for Halon or HFC-227BC.

(U) It should be noted that a mix of Halon 1301 and dry chemical was evaluated previously in 

one live-fire test with reasonably good results. In that test, where a much lower fraction of dry 

chemical was used compared to the tests described herein, a significantly reduced acid level was 

measured compared to the test without the dry chemical (ref. 4). This is consistent with the 

findings reported herein where the amount of Halon 1301 required to successfully extinguish a 

fire was found to be reduced by a factor of more than two when mixed with dry chemical. This 

result needs to be verified with live-fire tests on application-representative vehicles.

(U) „Water+‟ consistently knocked the initial fire down but reflash was reliably prevented 

only when proprietary developmental nozzles were used. Dry chemical systems did relatively 

well when higher-than-currently accepted concentrations were applied but were more prone to 

reflash than all the other agents except „Water+.‟ The higher levels of dry chemical are probably 

safe for occupied areas but may pose unacceptable operational limitations; for example, a period 

of obscuration may last many seconds, and clean-up may be necessary more quickly than the 

current minimum acceptable delay of 48 hours.

(U) Earlier tests directed at understanding whether FK-5-1-12 is a viable Halon 1301 

replacement in crew AFES were conducted by TARDEC (ref. 24) and the National Research 

Council of Canada (ref. 25) using fast-growth fires. These tests yielded similar results: total acid 

levels were well above current USA incapacitation limits. The tests described herein confirmed

those results and extended them by using a wider range of agent concentrations, extinguisher 

technologies, and distribution nozzles. Although a custom nozzle developed for FK-5-1-12 in 

this application was used (ref. 25), further improvements in distribution may be possible. 

(U) Insight into why FK-5-1-12 performed relatively poorly in these and similar tests may be 

obtained by considering that other FK-5-1-12 tests were „total flooding‟ and used pan-fires, not 
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 14 of 17

fast-growth, explosive fire threats (see ref. 26 for example). Total flooding systems typically 

inert a protected volume with sufficient agent concentrations to prevent combustion, and the fires 

are typically small with respect to the protected volume. The tests reported herein matched 

relatively large, fast-growing fires with rapid but essentially local agent application, a very 

different scenario than typical total flooding. 

Figure 6. (U) Peak Acid levels for „HFC-227BC,‟ „FK-5-1-12+‟ and „FK-5-1-12‟ (ref. 13b) 

versus Agent a) Mass and b) Volume Concentrations. The solid lines in (a) are power curve fits. 

Note: Although the peak acid levels for „HFC-227BC‟ and „FK-5-1-12+‟ are similar, the 

integrated levels used in casualty assessments were very different: none of the FK-5-1-12-based

tests „passed.‟ 

(U) Fire protection professionals often evaluate suppression agents in terms of the required 

concentration (usually on a volume percent basis as in ref. 26). While comparisons based on 

concentration are valid and useful, it must be remembered that other agent properties such as 

required mass must be considered separately. Figure 6 compares peak acid levels measured (ref. 

13b) in „HFC-227BC,‟ „FK-5-1-12+‟ and „FK-5-1-12‟ tests versus mass and volume 

concentrations (ref. 16). Although the peak acid levels versus concentration for the agents are 

very similar, especially for the ‟HFC-227BC‟ and FK-5-1-12+,‟ the mass of agent that yields a 

given acid level is very different: far more „FK-5-1-12+‟ than „HFC-227BC‟ by mass must be 

delivered to achieve the same acid level. 

(U) Note that although the peak acid levels for „HFC-227BC‟ and „FK-5-1-12+‟ in Figure 6

are similar, the integrated levels used in casualty assessments were very different: none of the 

FK-5-1-12-based tests „passed,‟ as shown in Figure 3. The difference is related to the relative 

evolution in time of COF2 and HF. Halon and HFC-227BC tests with good fire suppression 

show COF2 quickly peaking and then slowly decaying as the HF level slowly rises; in FK-5-1-12

tests both COF2 and HF peak quickly and then slowly decay. The result is that the total 

integrated acid level used in casualty assessments (see Table 3) is higher in FK-5-1-12-based 

tests (ref. 13).
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 15 of 17

(U) As noted earlier, the tests described herein were conducted using a test box without 

significant clutter and at the ambient temperature at the test site. More comprehensive, vehicle 

level tests should address the effects of clutter and operation at temperature extremes (especially 

low temperatures).

(U) CONCLUSION

(U) Meeting current performance requirements for crew AFES in USA ground vehicles using 

alternatives to Halon 1301 and HFC-227BC tested to date will require some combination of 

invention, development and/or increase in space claim and weight compared to fielded systems.

The basic result is that, with current products, none of the alternate agents are drop-in 

replacements for Halon 1301 or HFC-227BC. However, a blend of Halon 1301 and dry 

chemical has been found to be about twice as effective as Halon 1301 alone. Thus, pending 

confirmation tests on vehicles, it may be feasible to use less Halon in legacy systems without 

compromising fire protection performance.

(U) Disclaimer: Reference herein to any specific commercial company, product, process, or 

service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or 

imply its endorsement, recommendation, or favoring by the United States Government or the 

Department of the Army (DoA). The opinions of the authors expressed herein do not necessarily 

state or reflect those of the United States Government or the DoA, and shall not be used for 

advertising or product endorsement purposes.

(U) ACKNOWLEDGEMENTS

(U) This program was funded by Ground Systems Survivability (GSS) at TARDEC and is a 

continuation of the work reported previously (ref. 27). Valuable support and discussions with 

Ron Sheinson of the Naval Research Laboratory and Joe Senecal of United Technology Fire & 

Security are gratefully acknowledged. The excellent support of Aberdeen Test Center‟s Poverty 

Island Range 12 team was crucial to completing these tests.

(U) REFERENCES

1. (U) A comprehensive description of armored vehicle fire protection approaches through 1995 

is given in “Military Handbook Design of Combat Vehicles for Fire Survivability,” MILHDBK-684.

2. (U) Early AFES components and development are described in Cinzori, R. J., “Dual 

Spectrum Infrared Fire Sensor,” IRIS, 15 June 1977.

3. (U) Koffinke, MAJ, “Real Time Battle Damage Assessments,” US Army, Ballistic Research 

Lab, on assignment in Desert Storm, 1991.

4. (U) McCormick, S. J., Clauson, M. and Cross, H., “US Army Ground Vehicle Crew 

Compartment Halon Replacement Program,” Halon Options Technical Working Conference 

(HOTWC), 2-4 May 2000.
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 16 of 17

5. (U) Hodges, S. E. and DiRaimo, L., “Automatic Fire Extinguishing System (AFES) Alternate 

Agent Integration Challenges,” Proc. 15th Annual Ground Vehicle Survivability Symposium 

(GVSS), April 2004.

6. Ryzyi, M., “Stryker Fire Suppression System Qualification,” Proc. 15th Annual Ground 

Vehicle Survivability Symposium (GVSS), April 2004.

7. (U) Hodges, S. E., “Challenges in Integrating Halon-Alternate Agents into Automatic Fire 

Extinguishing Systems (AFES),” Halon Options Technical Working Conference (HOTWC), 

2006.

8. (U) World Meteorological Organization (WMO) 1998, Model-Derived Method 

9. (U) Intergovernmental Panel on Climate Change (IPCC) 2001 Method, 100 Year ITH.

10. (U) “Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 

202(a) of the Clean Air Act, Climate Change Division, Office of Atmospheric Programs, US 

Environmental Protection Agency, 17 April 2009.

11. (U) Waxman and Markey, Reps., “American Clean Energy and Security Act of 2009,” US 

Congress, HR2454, 15 May 2009.

12. (U) “FTIR Methodology to Distinguish Novec 1230 and COF2 Spectra,” ATC Private 

Communication, March 2009. 

13. (U) ATC Chemistry reports: a) 2009-CC-167A, b) 2009-CC-222, c) 2009-CC-227, d) 2009-

CC-359, e) 2009-CC-825.

14. (U) a) Many current requirements are based on Ripple, G. and Mundie, T., “Medical 

Evaluation of Nonfragment Injury Effects in Armored Vehicle Live Fire Tests,” Walter Reed 

Army Institute of Research, September 1989. b) The minimum oxygen level is found in 

Swanson, G., “Fire Survivability Parameters for Combat Vehicle Crewmen,” Memo to the 

US Army Surgeon General, 20 February 1987. c) Acceptable Noise Levels for this 

application are defined in section 6-2c(2) of “Hearing Conservation Program,” US Army 

Pamphlet 40-501, 10 December 1998.

15. (U/Limited Distribution) Januszkiewicz, A. J. and Davis, E. G., “Evaluation of Potential 

Physical Injury from Mechanical Forces Due to Automatic Fire Extinguisher System 

Discharge in the STRYKER Combat Vehicle: An Initial Assessment and Recommendations 

to Prevent Injury,” Walter Reed Army Institute of Research, 21 August 2003.

16. (U) “NFPA 2001 Standard on Clean Agent Fire Extinguishing Systems 2008 Edition,” 

National Fire Protection Agency (NFPA), Quincy, MA, 15 August 2007.

17. (U) See for example: Rabash, D. J., “Quantification of Explosion Parameters for 

Combustible Fuel-Air Mixtures,” Fire Safety Journal, v11, ps 113-125, 1986. The volume 

factor is discussed in Eckhoff, R. K., “Use of (dP/dt)max from Closed-Bomb Tests for 

Predicting Violence of Accidental Dust Explosions in Industrial Plants,” Fire Safety Journal, 

v8, ps 159-168, 1984/85.

18. Moore, P. E., “Suppressants for the Control of Industrial Explosions,” J. Loss Prev. Process 

Ind., v9(1), ps. 119-123, 1996.

19. (U) Dessicarb is described in: “DXP-1 - US/Canada Version,” MSDS KA012, Kidde 

Aerospace & Defense, 12 October 2007. 

20. (U) “Toxicity Evaluation of Acute Exposure to Dessicarb,” US Army Environmental 

Hygiene Agency, Toxicological Study No. 75-51-Y1F8-94, October 1993.

21. (U) Robert G. Daniel, R., and Skaggs, R., “Test Report: Light Attenuation by Powder Fire 

Fighting Agents,” ARL Report for Tests 03-14 August 1998, 1998.

22. (U) Potassium-bicarbonate-based dry chemical, also known as „Purple K‟, is described in 

http://www.nrl.navy.mil/content.php?P=PURPLEK
UNCLASSIFIED NFPA SUPDET 2010

UNCLASSIFIED page 17 of 17

23. (U) Reed, M., Fleming, J., Williams, B., Sheinson, R, Chattaway, A., Laverty, N., Spring, D., 

“Laboratory Evaluation of Bicarbonate Powders as Fire Suppressants,” Proc. International 

Conference of Ozone Protection Technologies, pp. 333-344, 1997.

24. (U) ATC Chemistry Report 2009-CC-016 reports June 2008 test results. 

25. (U) See Table 4.1 in Kim, A., Crampton, G. and Kanabus-Kaminska, M., “Evaluation of Gas 

Generator System with NOVEC 1230 Agent as a Replacement for Crew Compartment 

Protection Halon System,” National Research Council Canada, Report B-4193.1, 31 March 

2008.

26. (U) Ditch, B., Rivers, P. and Thomas, S., “A Continuation of Thermal Decomposition 

Product Testing with C6 F-Ketone, Increased Concentrations,” Halon Options Technical 

Working Conference (HOTWC), May 2002.

27. (U) Hodges, S. E. and McCormick, S. J., “Evaluation of Fire Suppression Agents for 

Protection of Occupied Spaces in Military Ground Vehicles,” Proc. Ground Vehicle 

Survivability Symposium (GVSS), August 2009.